1. Field of the Invention
The present invention relates to a light-sensitive device having a color filter such as a color solid image sensor and a spectrum detector for spectroscopic measurement. The term "a light-sensitive device" means a detector that responds to radiant energy.
2. Description of the Prior Art
A light-sensitive device having color filters has been proposed wherein color filters of organic film are applied directly on the surface of a chip of light-sensitive device of semiconductor, each of which is made from a dye base material such as gelatin, casein or polyvinyl alcohol having been dyed. In such a prior art light-sensitive device, filters of on-chip type are applied directly on the surface of a chip of a light-sensitive element. The filter comprises three kinds of color filters which transmit lights of red, green and blue, respectively. Each of the three color filters is arranged on one of the surfaces of three light-receiving parts of the light-sensitive element so that the color distribution of a light to be received can be measured. An infrared rays cut-off filter is arranged in front of the light-sensitive element in order to cut off light components in the infrared region. A diffuser plate is arranged in front of the infrared rays cut-off filter in order to disperse an incident light to be detected so as to make the color distribution uniform on the surface of the light-sensitive element. Such a light-sensitive device having the color filter of on chip type as mentioned above has advantages of simple structure and low cost when compared with a light-sensitive device wherein three color filters are positioned and stuck individually on a chip.
An above-mentioned color filter made of organic film having been dyed has a disadvantage in that the dye base material and dyes deteriorate and fade out by ultraviolet rays so as to cause secular changes in the spectroscopic characteristics thereof. Therefore, it is necessary to put an ultraviolet rays cut-off filter in front of the color filter.
Further, a prior art color filter of organic film having been dyed is inferior in heat resistance. Therefore, when such a color filter is used as a color filter for a light-sensitive device, restrictions on heating it should be taken into account during manufacturing processes to be carried out after the color filter has been applied. That is, since, in the manufacturing processes of a semiconductor light-sensitive device having a color filter, assembly processes such as die bonding, wire bonding and resin molding accompanied with heating the color filter should be done after mounting it, thermal conditions in individual processes are restricted due to the heat resistance of the color filter.
Still further, a prior art color filter of organic film dyed is inferior in moisture resistance because the dye is soluble in water generally.
Further, ammonium bichromate is added usually in order to assist dyeing in a dyeing process of dye base material such as gelatin, casein or polyvinyl alcohol with a dye. Thus, waste liquor should be processed because heavy metals are contained in the waste liquor.
As is apparent from the fact mentioned above, it is desirable to employ such a wire bonding process of a semiconductor chip element that does not need heating. Among conventional wire bonding processes, a supersonic process does not need heating of a substrate especially because bonding wires of aluminum is bonded under ultrasonic vibrations. However, this method has a disadvantage in that bonding strength obtained is not enough since aluminum wires used as bonding wires have a relatively large surface roughness and are liable to corrode.
All of other wire bonding processes such as thermocompression bonding process, thermosonic process and laser process accompany heating. In thermocompression and thermosonic processes, gold wires or copper wires are used as bonding wires, and they are bonded to a chip due to heat and load in the former process and due to heat, load and supersonic vibrations in the latter process, respectively. Thus, both of these processes inevitably accompany the heating of a substrate. The temperature of the heated substrate is between 300.degree. and 350.degree. C. in the thermocompression process and between 150.degree. and 250.degree. C. in the thermosonic process. Because the thermocompression process needs a higher temperature than the thermosonic process, the former
so often recently. On the other hand, the thermosonic process needs heating of the substrate up to a temperature between 150.degree. and 250.degree. C. though the temperature is lower than the counterpart of the thermocompression process. If an element to be bonded is only a silicon semiconductor chip, there arises no thermal problem practically. However, if components of lower heat resistance are applied on the chip, they are liable to deteriorate in the bonding process. Laser bonding process wherein a laser beam is irradiated on a spot to be bonded also accompanies heating.
If a light-sensitive device having the color filter of organic film as mentioned above can be bonded to electrical connection parts by using a wire bonding process accompanying heating, a light-sensitive chip element can be provided at a low cost and at a high package density.
However, a wire bonding process which needs heating the substrate up to a temperature mentioned above cannot be used for a prior art color filter of organic film of low heat resistance. In other words, a prior art color filter, which is prepared by dyeing a dye base material such as gelatin, casein or polyvinyl alcohol with a dye, deteriorates at a temperature lower than the above-mentioned operating condition of temperature because these materials have low heat resistance (at about 140.degree. C. at most), and characteristics as a color filter are varied.
Resin molding method has been used widely for packaging a semiconductor device. Packaging with use of resin molding method has advantages such as good moisture resistance, high reliability and low cost. Because the operating condition of temperature during the resin molding process is between 150.degree. and 180.degree. C., no problems occur practically if an object to be packed is only a semiconductor chip of silicon.
A reliable and inexpensive device will be provided if an above-mentioned light-sensitive chip having a color filter of organic film of on-chip type could be molded with transparent resin by using the above-mentioned resin molding method. Further, a reliable and inexpensive device which needs no diffuser plate will be provided if a milk-white resin is used in the resin molding process instead of transparent rein. However, the resin molding process which needs the above-mentioned operating condition of temperature cannot be adopted because a prior art color filter of organic film has low heat resistance as mentioned above.